Monday, 4 September 2017

When converting data from one model to another, there is often the thought over whether it would be beneficial to use automapper or whether factory methods should be used to explicitly convert between models. I'm going to explain what each of these is, and explain a couple of advantages and disadvantages of each.

Automapper

Automapper is a NuGet package that allows you to "get rid of code that mapped one object to another". It is convention based, and if there are a large number of properties that are identical on 2 classes it can save a lot of developer time converting between objects. It also means that less code can be written for this conversion... Yay! However, there are a couple of disadvantages that come with convention based as opposed to explicit programming, and Automapper is no exception!

If you are using Automapper with default mappings and refactor the name of the source/target model, then you won't necessarily know until runtime because it won't cause a compile time error. The issue is that if there is a rename of the property, automapper will no longer be able to map correctly. Whereas if you were to explicitly code the conversion, there would be a compile time error so you can identify the error earlier. The risk of this failed mapping occurring can be mitigated by unit testing the mapping.

A similar issue to this is that there is a lack of static analysis. For example, if you find all references of a property it may look like nothing is referencing that property so you may be tempted to remove it. However, automapper could be mapping to this property without you even realising.

Overall, Automapper is a well tested library that can save you time writing uninspiring conversion code, but there are downsides and different scenarios may mean that it is beneficial or not.

Factory Methods

Factory methods allow you to explicitly convert between objects. Due to the explicit conversion, it is easy for developers working on the same project to see where values are coming from. This is because it is not hidden behind a library that the developer may or may not be familiar with. It is also easier to debug. If mapping is done incorrectly there will also be compile time errors which can help catch issues earlier.

Of course, there is a reason the Automapper NuGet package exists and this is because the manual conversion is tedious and takes time that could be spent on other things. The manual conversion also means that there is more code sitting in your project. Additionally, with anything manual there is the chance of human error and 2 properties that don't actually align with each other could potentially be mapped. Your unit tests should pick this up though.

When trying to choose between Automapper and Factory methods, think about your code and how well the objects will map automatically without configuration. Secondly, consider the important of static analysis and compile time errors in your code. This isn't a one-size fits all comparison, it's case by case as to which will be beneficial!

Friday, 1 September 2017

Extension methods allow you to extend functionality of a specific type. It is a special kind of static method that you can call as if it were an instance method on the object of the specified type. Extension methods are simple to define and you can define them as follows:

NuGet packages are extremely useful way to add libraries/components to your code base. This is similar to the traditional way of referencing DLLs except that you get notifications when there are updates.

You may find that if your code lives in separate Git repositories that if someone wants to use a project from one Git repo in another Git repo that they would need to download both. However, NuGet packages can be stored in a common location e.g. the NuGet Package Gallery which is available to all, or on a centralised private NuGet server. If you want to use a private NuGet server, you will need to add a package source in the NuGet package manager. You can do this by clicking the little cog next to "Package source".

Now for actually generating the NuGet package you can do this automatically on build, by opening a right clicking on a project and selecting properties. Then navigate to the "Package" tab and check "Generate NuGet package on build"

Tuesday, 15 August 2017

Payments and Financial Reports

You can go here to review your confirmed sales for closed months. It will give you a breakdown by currency and an estimated conversion.

Sales and Trends

This will show you a graph of your sales. You can see which apps have sold, and roughly how many proceeds you have.

When will I get paid?

Payments for a lot of countries will be after you've earned $10 USD. Some countries require a minimum payment threshold of $150 USD. The payment will happen approximately 30-45 days after the financial reports for the month in which you reached the minimum payment threshold. The payment will be made to your designated bank. You can read more about it on Apple's "Getting Paid" Resources and Help page. If you meet these criteria and you haven't received a payment, you may want to check that your bank account details have been supplied under "Agreements, Tax, and Banking". You should also check that you have a valid contract with Apple as this will also cause payments to be held.

Friday, 21 July 2017

Sometimes when you are storing sensitive information in the App.config e.g. API keys or database connection strings, you don't want to store them in plain text. Fortunately, visual studio provides a command line tool that enables you to encrypt sections of your App.config. These are automatically decrypted by the ConfigurationManager when you try to access the settings.

Create a copy of your App.config called web.config. This is because the command line tool you will use to encrypt your settings will look for a web.config.

Open the Developer Command Prompt for VS

Enter the following command:

aspnet_regiis -pef [section to encrypt] [path containing web.config]

Copy the contents of the web.config into the App.config.

It is best that you have a separate section from appSettings for your encrypted settings as this will mean you will be able to change plain-text settings e.g. API URLs or retry attempts, without having to go through the encryption process. To create this section your App.config before encryption could look as follows:

Thursday, 18 May 2017

When you call an asynchronous method from your Main method of a console application in C#, you may experience the situation where your program runs to completion without hitting breakpoints following an await. An example of this is below:

Tuesday, 9 May 2017

The Code

Polling services can be incredibly useful for picking up when something has changed and performing some actions. This post will cover how to set one up in C#. Firstly, you will want to create a new project with type Windows Service in Visual Studio:

You will then want to rename Service1.cs and all its references to be something more representative of your polling service. You will also want to update the name the polling service will appear with by clicking on Service1.cs to open the designer, and then right click within the designer and choose "Properties", then update ServiceName in the Properties view.

In order to view the code backing the polling service you can click on "click here to switch to code view" from within the designer. This code should look something like this:

You can put whatever you want in ProcessThings but personally, I add a console application project to the solution that handles all of the processing. This way I can debug it at will without the need to install the polling service/wait for the polling period.

Installation

Click on Service1.cs, then right click and choose "Add Installer", you can name serviceProcessInstaller1 and serviceInstaller1 whatever you like. Click on serviceProcessInstaller1 and select what account you would like the polling service to run with, I chose Local System which is quite common, and means that it is using the local user's account. After this you can build your project. To install it open the Developer Command Prompt for VS 2017 as an administrator and then navigate to where the .exe of your project is.

Monday, 8 May 2017

Babel is a dependency that React Native has. Babel lets you write ES2016/ES6 and then it converts this to JavaScript (ES5) that will run on your browser. This is because at the current point in time, the latest version of all major browsers have interpreters that can interpret ES5.

ES2015 adds syntactic sugar to ES5, that can result in faster JavaScript development. It can also result in tidier more readable source code, although of course readability is heavily opinion based so ES6 syntax may not be for everyone. It aims to tackle some of JavaScript's shortcomings addressed by TypeScript/CoffeeScript. This means you can write lambda expressions, JSX, and other syntax available in ES2015.

To write ES2015 in React Native apps you don't need to do any additional work as it is configured by default. However, you can write straight JavaScript if you want to.

References

Tuesday, 4 April 2017

When you make a cross domain request from your website you may have your request fail. One of the potential causes for this is that the API you're calling does not handle preflight requests. You will know that this is the case because you will see an OPTIONS request to the API you made the call to, but this call will fail and no subsequent GET/POST/PUT or whatever other HTTP call you were trying to make will be made.

What's the point?

Preflight requests arose as CORS made it possible to specify more headers and requests methods in a request than was previously possible to make cross origin. This meant that some servers were developed under the assumption that they would not receive these cross-origin requests and would thus be protected from them. A preflight request provides a way for the server to opt into receiving these requests, as the server must respond to the OPTIONS request with the types of methods, headers, and origins that it accepts. This protects the server (particularly older servers), without the need for the server to change as if it doesn't respond to the OPTIONS request with headers that match the request, then the subsequent request will not be made.

Note: not all HTTP requests will have a preflight request. If the request was possible cross-origin prior to CORS, then a preflight request will not be made as older servers should have handled any security around these requests themselves.

How to get the preflight request to succeed?

Assuming that the server responds to the OPTIONS request successfully, the website should not need to make any further changes as the further requests will be handled by the browser. So if you are using a publicly exposed API and your request is failing on the OPTIONS request, you will need to confirm that the API is accepting your domain, headers and method you submitted the request with. You can do this by checking the OPTIONS response meets the following criteria:

Access-Control-Allow-Headers header with comma-separated list of headers you made your request with

Access-Control-Allow-Origin header with * or domain matching that which you are making the request from

Access-Control-Allow-Methods header with comma-separated list of methods you can access the endpoint with

Status is 200

If you want to enable your API to handle preflight requests, then you will need to be able to accept and OPTIONS request and respond to the requester with the above headers/status. The actually implementation of this will be down to the technologies you have developed your APIs using but there will commonly be APIs available to enable CORS. Note: your API that is available due cross-domain will also need to have GET/PUT/POST etc, with these headers.

References

Monday, 3 April 2017

Previously, we discussed how we can make reusable components by passing data to a component using props. State can also be used to help us provide data to a component. However, the difference is that state is used to hold values that change, and when it changes it will trigger updates to the components that reference it. State should generally be initialised in the constructor, and set state should be used to update it.

As a simple example, consider a UI that has a text input for the users name and then a text component that greets them, it would appear as follows:

Friday, 27 January 2017

When developing using React Native, we reference two separate libraries (both React and React Native).

React

React is more generic and also used on the web, essentially it ensures all the components work together. It is also responsible for understanding how components should behave. Any components you define will extend Component which is defined by React.

React Native

Provides the default core components that translate to native components. It can take a component and place it on the mobile phone's screen. It is basically the link between your Javascript and the mobile device.

Thursday, 26 January 2017

ESLint is a tool that analyses your JavaScript for potential errors and can be installed into many common text editors. This can help you pick up errors in your JavaScript without reloading your website or react native app, which can help you increase your productivity... YAY!

ESLint has a few setup layers - this is split into editor specific config and project specific config. This means we can configure which ESLint rules to validate our code using on a project by project basis. There are some preset configurations for this so that as a developer you don't need to add rules one by one.

Tuesday, 24 January 2017

In React Native, to add navigation to your app you can use the Navigator component. You can have as many navigators as you want in your app e.g. you may have one for your whole app or multiple if you are using tabs with different navigation stacks for each tab. This tutorial will explain how to add a single navigator to your react native app. Firstly, add the navigator as the base for your application so specify it in the index.ios.js and the index.android.js:

// Import the Navigator from React Native
import React, { Component } from 'react';
import {
AppRegistry,
Navigator
} from 'react-native';
import MainScene from './app/scenes/mainScene'
import AddGoalScene from './app/scenes/addGoalScene'
export default class Goalie extends Component {
renderScene(route, navigator) {
// Specify the properties to pass to the scene you will
// render. It is useful to pass the navigator around the
// scenes so that you can push and pop to the navigation
// stack.
var globalNavigatorProps = {
navigator: navigator,
goal: route.goal
};
// Based on the route passed to the navigator you can
// determine which scene to render.
switch(route.ident) {
case "MainScene":
return ( <MainScene {...globalNavigatorProps} />);
case "AddGoalScene":
return ( <AddGoalScene {...globalNavigatorProps} />);
default:
return ( <MainScene {...globalNavigatorProps} />);
}
}
render() {
return (
// Render your navigator
// You must specify an initial route, which will become
// your root view for the app. The initialRoute is just
// an object with an identifier you can use to define
// which screen should be displayed, and whatever other
// info you would like to pass in.
// You must also specify a renderScene function which
// has the args route and navigator, this must return
// what you would like to render on the navigation stack.
<Navigator
initialRoute={{ident: "MainScene", goal: "MainScene" }}
renderScene={this.renderScene} />
);
}
}
AppRegistry.registerComponent('Goalie', () => Goalie);

The next step is to be able to add and remove from the navigation stack. For simplicity, I will demonstrate this using back and forward buttons:

Monday, 16 January 2017

One awesome thing about React Native is that you can use the npm to install packages which allow you to reuse JavaScript code that someone else has written(see here for list of packages)! This post will take you through how to install/uninstall packages.

Installing Packages

First, you will need to find a package you would like to install on the npm website. Once you find a package, go to your react native project's folder in the terminal and type:

npm install react-native-checkbox-field --save

--save means that the module you are installing will be automatically added to your package.json's dependencies. If you don't want your package.json to update, leave off the --save. After completing the install and updating your package.json, you can then use your new package as described on the packages page on the npm website, e.g:

import { CheckboxField, Checkbox} from 'react-native-checkbox-field';

Uninstalling Packages

Uninstalling packages is similar to installing packages. Go to your react native project's folder in the terminal and type:

npm uninstall react-native-checkbox-field --save

--save means that the module you are uninstalling will be automatically removed from your package.json's dependencies. If you don't want your package.json to update, leave off the --save. After completing the uninstall and updating your package.json, you will no longer have access to the package you have uninstalled so you should remove all references to it.

Thursday, 12 January 2017

Laying out components in React Native is done using flexbox, the key difference though is that style names are written camelcase e.g. background-color would be backgroundColor when defining it as part of a React Native Stylesheet. Today, I'll take you through the key ways you can layout your components using flexbox:

Parent Properties

display: flex;

In web dev, if you want to layout your page using flexbox you will need to specify "display: flex;" in your style for that HTML element. However, in react native this is unnecessary.

flexDirection

row (default): layout child components left to right

row-reverse: layout child components right to left

column: layout child components top to bottom

column-reverse: layout child components bottom to top

flexWrap

nowrap (default): components try to fit on one line

wrap: components can wrap onto new line (left to right)

wrap-reverse: components can wrap onto new line (right to left)

flexFlow

Shorthand for flexDirection and flexWrap e.g. column wrap

justifyContent

Distributes space left over once all the child items have been rendered.

flex-start: components are rendered at the start of the parent

flex-end: components are rendered at the end of the parent

center: components are rendered at the center of the parent

space-between: components are rendered equidistant apart, with a component aligned with both the start and end of the parent component

space-around: components are rendered equidistant apart, with a space at before the first and last component

alignItems

How components are aligned vertically for row layout or horizontally for column layout:

flex-start: aligned with the top of the parent layout for row, and with the left of the parent for column

flex-end: aligned with the bottom of the parent layout for row, and with the right of the parent for column

Wednesday, 11 January 2017

In this post, I will take you through how to create a component that is reusable in iOS/Android. First off, we will make a folder where we place all our reusable code, I have called it app and created it under the folder that was created when using the react-native command to initialise your app. There will be a few different things that go in this folder, so I have created another folder under app called components.

ViewContainer Component

I have chosen a simple component for the purpose of this tutorial, and it is a ViewContainer component. It is effectively a react native view, with specified styling applied and will form the base of all the screens you add to your app. Under app/components I add a new folder called viewContainer with 2 new files, the first file defines how the component is rendered and is called viewContainer.js:

The first file imports React and Component, React is a default export (see here for explanation) and so doesn't need to be in {}. We import Component so that we can define a new component and how it is rendered, this is defined in the render function. We also import View from react native, as this is the type of existing component we want to base our custom component off. And finally, we also import the style for the view container which is called style.js:

Monday, 9 January 2017

Hi everyone, React Native is a cool framework I've been learning about lately that lets you build mobile apps using Javascript. So over the next few weeks I will document my efforts with developing apps in React Native!

Getting Started

Just follow the React Native Getting Started guide to download everything you require. Note: iOS apps can only be developed on a Mac. I will be developing an app for both Android and iOS over this series so will be using a Mac. If you get errors, you may need to update node/npm if you have previously installed these.

Initialising the App

In your terminal, change to your development directory or where you want your react native project to be saved.

Enter the command

react-native init [project_name]

This will setup your React Native project

Enter the command

cd [project_name]

Enter the command

react-native run-ios

from inside your React Native project directory to see the base iOS output

To see the base Android output:

Open the android folder in Android studio

Go to Tools > Android > AVD Manager and setup a device, this will handle installing anything you need for the emulator to run

Run the virtual device you created

Enter the command

react-native run-android

from inside your React Native project directory to see the base Android output

Editing the view

You can edit the view displayed in the index.android.js and index.ios.js files in your preferred text editor.

GameKit makes it really easy to add global scoreboards to an app, where you can compare yourself to Game Center friends or everyone who has played on the all time scoreboard. This article will take you through how to add it to your apps.

Initial Setup

First, go to iTunes Connect and select your app, and then click features. It should look something like this:

Then click on the plus next to leaderboards and select "Single Leaderboard". You should now be at a page that looks like this:

Fill out the fields, the Leaderboard Id will be how you reference it in the code. Ensure you also add a language, the name here will be the name that appears to users viewing your scoreboard:

Once you are done click save, and ensure that Game Center is enabled for your app against the build you are setting up. Then you will need to also enable it via Xcode. Open Xcode and ensure that GameKit is added as a Linked Framework/Library:

Finally, check the capabilities to ensure Game Center is successfully enabled:

Coding a Leaderboard

First, ensure the user is logged in when they first open the application by authenticating the player in the viewDidLoad function on one of the initial ViewController's presented by the application. Ensure the state of whether game center is enabled or not is saved, as this will allow you whether to show the option to view leaderboard after a user has played your game. For convenience and code simplicity, gameCenterEnabled is a global variable in this example.

Next, you will want a view with a button to show the leaderboard , the view controller for this view should implement GKGameCenterControllerDelegate and handle dismissal and opening of the leaderboard. In this example saving of the score happens here as this view is displayed upon game completion. However, saving of the score can happen anywhere in your application.